“Carbo Loading” is a term often heard around athletic circles, and in fact is used by many athletes in many different sports. However the true definition and method of carbohydrate loading is poorly understood, and it may disappoint some to realise that having a pasta meal on the night before an event is not Carbohydrate Loading! In fact to carbohydrate load effectively, you must make changes to both your nutrition and your training!


What is “Carbohydrate Loading”?

The whole idea behind Carbohydrate Loading is to avoid running out of energy during aerobic exercise by ensuring you begin with maximum storage levels of Glycogen. Carbohydrate Loading is a strategy used by athletes to help maximise muscle glycogen stores prior to endurance events.

Carbohydrates are arguably the most important source of energy for athletes because once digested, the carbohydrates are broken down into smaller sugars (eg glucose) that are used for immediate energy, and any glucose not needed immediately is stored as glycogen. Once glycogen stores are full, any extra is then stored as fat. Carbohydrates are critical for the following reasons:

  1. Glycogen is the most common source of energy, so is critical for all short, intense bouts of exercise as it can be broken down instantaneously and is immediately accessible.
  2. During longer, slower duration activities, fat becomes an important source of energy, however glycogen is still needed to break the fat down into a format that can be used by the body for energy.
  3. If there is insufficient carbohydrate, the body must break down protein to make glucose for energy. Protein plays an essential role as a “building block” for many body tissues, including muscle, bone and skin, so to use protein for energy limits our ability to maintain the integrity of these tissues and can lead to injury.

carbo-loadingIt is for the reasons above that “Carbohydrate Loading” is popular with athletes. What Carbohydrate Loading aims to do is to maximise the muscles stores of glycogen prior to participating in endurance events. Originally developed in the late 1960’s, Carbohydrate Loading has been refined dramatically to the process it is today. Originally, the process involved a “Depletion Phase” whereby the athlete trained excessively hard whilst on a low carbohydrate diet, followed by a “Loading Phase” of low training and high carbohydrates. The thought behind this was that if you made the body crave glycogen through low storage levels, it would then rapidly and excessively store glycogen throughout the Loading Phase. Thankfully (for athletes) the Depletion Phase has been proven to be unnecessary, as it used to make training very difficult (and injury risk higher) when exercising on such low energy levels.

How Do I Carbohydrate Load?

To begin with, it is important to realise that Carbohydrate Loading is really only effective in events that involve continuous exercise at moderate to high levels of intensity for 90 minutes or greater. Shorter duration exercise is not likely to benefit as the body should have sufficient natural reserves of glycogen. In shorter duration events such as 100m and 200m sprints, the athlete is probably relying purely on anaerobic energy sources. Events from 1500m upwards tend to be largely aerobic, using glucose as the primary energy source. Once the event gets above 90 minutes duration, fat as well as glucose becomes an important energy source.

The tapering phase of a training program is essential  to the whole Carbohydrate Loading process, as you don’t want to be burning off the extra energy that you are trying to store! However there is also a fine balance to ensure that you are not taking in too much carbohydrate for too long, at a time of low intensity training, as this could result in unwanted weight gain in the days prior to the event.

Therefore the ideal time to begin your loading is 24 – 72 hours prior to your event. For long duration events like a marathon, it is recommended that your carbohydrate intake is 10 – 12g per kg of body mass. However you also need to be careful that your increased carbohydrate intake does not include high fibre intake or this can alter your bowel habits during the event! Refined carbohydrates such as honey, jam, sugar, sports drinks, cordial, fruit and lollies are all low fibre carbohydrate sources. Complex carbohydrates, which take longer to digest, include bread, rice and pasta – the commonly known constituents of a carbohydrate loading regime.

Why Do Most people Fail At Carbohydrate Loading?

Probably the greatest reason for failure results in athletes not seeking professional advice to develop a program that is suitable for their own body and sporting requirements. However there are some other common reasons for failure of a Carbohydrate Loading Program:

  • Many athletes find it difficult to back off training in the days prior to an event. The tapering phase is a crucial component.
  • Many athletes simply don’t take in enough carbohydrate to “load” sufficiently. This is where the guidance of a dietitian is needed.
  • Taking in the wrong carbohydrates (that are high in fibre) can lead to drastic stomach or bowel upsets during an event.
  • Fear of gaining weight during the tapering phase can cause athletes to reduce their carbohydrate intake below required amounts.

 Whenever dealing with a Carbohydrate Loading program, there are numerous individual requirements that must be taken into account, therefore it is important that anyone considering a program such as this should consult a Sports Dietitian for specific advice.